Related papers: Adding quark spin effects to PYTHIA string fragmen…
We performed feasibility studies for various single transverse spin measurements that are related to the Sivers effect, transversity and the tensor charge, and the Collins fragmentation function. The processes studied include semi-inclusive…
Virtual photons have both the transverse and longitudinal polarization. In the inclusive DIS the impact of longitudinal photons, quantified by R=sigmaL/\igmaT sim 0.2, is marginal, but in diffractive DIS with excitation of small mass…
We analyze the left-right asymmetry in the semi-inclusive deep inelastic scattering (SIDIS) process without introducing any weighting functions. With the current theoretical understanding, we find that the Sivers effect plays a key role in…
HERMES has measured azimuthal single-spin asymmetries of charged pions produced in deep-inelastic scattering of positrons on a transversely polarised hydrogen target. The presented azimuthal moments provide access to two yet unknown quark…
The recent data on the transverse single spin asymmetry $A_{UT}^{\sin(\phi_h+\phi_S)}$ from HERMES and COMPASS Collaborations are analysed within LO parton model with unintegrated parton distribution and fragmentation functions. A fit of…
Azimuthal single-spin asymmetries (SSA) in semi-inclusive electroproduction of pi-mesons and charged K-mesons in deep-inelastic scattering of positrons and electrons on a transversely polarised hydrogen target were observed. Significant SSA…
We analyze the electroproduction of pseudoscalar mesons within the handbag approach. To investigate these reactions, we consider the leading-twist contribution together with the transversity twist-3 effects that are crucial in the…
The main goals of `spin physics' are recalled, and some theoretical and phenomenological aspects of longitudinally polarized deep inelastic scattering and other hard processes are reviewed. The spin dependent parton densities of protons and…
The production of D mesons in the scattering of transversely polarized protons off unpolarized protons at RHIC offers a clear opportunity to gain information on the Sivers gluon distribution function. D production at intermediate rapidity…
The study of transverse spin effects is part of the scientific program of COMPASS, a fixed target experiment at the CERN SPS. COMPASS investigates the transversity PDFs in semi-inclusive DIS, using a longitudinally polarized muon beam of…
We study charm production in ultra-relativistic heavy-ion collisions by using the Parton-Hadron-String Dynamics (PHSD) transport approach. The initial charm quarks are produced by the Pythia event generator tuned to fit the transverse…
Recently HERMES has observed an azimuthal asymmetry in electro-production of neutral pions in semi-inclusive deep-inelastic scattering of unpolarized positrons off longitudinally polarized protons. This asymmetry (like those observed in the…
We calculate the spin density matrix of the hadron $h$ created via quark fragmentation in the process $e^-e^+ \to q\bar q \to h + X$. In the case of $h=\Lambda$ the experimental data could possibly elucidate the problem of $s$-quark…
Dihadron Fragmentation Functions (DFF) provide a vast amount of information on the intricate details of the parton hadronization process. Moreover, they provide a unique access to the "clean" extraction of nucleon transversity parton…
We report the first measurement of target single spin asymmetries of charged kaons produced in semi-inclusive deep inelastic scattering of electrons off a transversely polarized $^3{\rm{He}}$ target. Both the Collins and Sivers moments,…
Identified hadron production is essential for the study of nucleon structure and QCD hadronization at high energies. We present the first calculation of unpolarized semi-inclusive deep-inelastic scattering (SIDIS) at…
Predictions are made for single spin azimuthal asymmetries due to the Collins effect in pion production from semi-inclusive deeply inelastic scattering off transversely and longitudinally polarized targets for the HERMES and COMPASS…
We point out that measuring longitudinal polarizations of different hyperons produced in lepton induced reactions are ideal to study the spin transfer of the fragtmenting quark to produced hadron in high energy hadronization processes. We…
A recent global QCD analysis of jet production and other polarized scattering data has found the presence of negative solutions for the gluon helicity distribution in the proton, $\Delta g$, along with the traditional $\Delta g > 0$…
COMPASS is a fixed-target high energy physics experiment at the SPS at CERN \cite{Abbon:2007pq}. One of the important objectives of the experiment is the exploration of the transverse spin structure of the nucleon via spin dependent…